A US study showing a link between omega-3 fish oils and prostate cancer is inconclusive, the organisation representing UK supplement manufacturers has said.

The research from Ohio State University, published in the Journal of the National Cancer Institute, found omega-3 fatty acids from oily fish increased the risk of high-grade disease by 71%.

Omega-3 supplements are popular because of their supposed health benefits, including protecting against heart disease and arthritis.

Each year Britons spend £116 million on fish oil supplements.

The Health Food Manufacturers' Association (HFMA) said the findings contradicted those of a large scale 2010 study which found no evidence that high levels of fish consumption increased the risk of prostate cancer.

The same study found a 63% reduction in risk of death from prostate cancer among men who ate large amounts of fish.

Dr Michele Sadler, the HFMA's scientific adviser, said: "This type of evidence can indicate an association, but does not demonstrate cause and effect."